中文摘要：

在东北半干旱地区的科尔沁沙地,秋冬与冬春季节由温度变化引起的土壤冻融对CO2排放具有显著影响,研究水分和冻融的交互作用对土壤呼吸的影响具有重要意义。以科尔沁沙地樟子松疏林草地、农田和草地为研究对象,通过冻融模拟实验分析水分和冻融循环对不同土地利用方式土壤呼吸的影响。结果表明,水分条件、土地利用方式和冻融循环均对土壤呼吸影响显著。冻融前草地土壤呼吸显著大于疏林草地和农田,冻融期疏林草地土壤呼吸显著大于农田,而冻融后草地土壤呼吸速率显著大于疏林草地。80%田间持水量时3种土地利用方式的土壤呼吸速率显著大于60%田间持水量时土壤呼吸速率;在培养期内（20d）,60%田间持水量时疏林草地、农田和草地的土壤CO2释放量分别为21.535、19.908和25.037gCO2·m-2,80%田间持水量时分别为26.407、29.447和36.246gCO2·m-2。

英文摘要：

In Horqin Sandy Land, a semiarid region of Northeast China, soil freeze-thaw caused by the temperature change in late autumn, winter, and early spring has significant effects on soil CO2 emission, and thus, it is of significance to study the effects of the interaction between soil moisture content and freeze-thaw on soil respiration. Taking the silvopasture system, cropland, and grassland in Horqin Sandy Land as test objects, a simulation experiment was conducted to study the effects of soil moisture condition and freeze-thaw cycle on the soil respiration under dif- ferent land use patterns. The results showed that soil moisture condition, freeze-thaw cycle, and land use pattern all had significant effects on soil respiration. Before freeze-thaw, the soil respira- tion rate was significantly higher in grassland than in silvopasture system and cropland. During freeze-thaw, soil respiration rate was higher in silvopasture system than in cropland. After freeze- thaw, soil respiration rate was significantly higher in grassland than in silvopasture system. When the soil moisture content was 80% of water-holding capacity （ WHC ） , soil respiration rate was significantly higher than that when the soil moisture content was 60% of WHC. During the whole incubation period （20 days）, the amount of soil CO2 emission from silvopasture system, crop- land, and grassland under 60% of WHC was 21. 535, 19. 908, and 25. 037 g CO2 ~ m-2, and that under 80% of WHC was 26. 407, 29. 447, and 36. 246 g CO2 ~ m-E, respectively.